"Davy, in the light of the fuller knowledge he obtained from Gay Lussac and Thenard's paper in the "Mem. d’Arcueil"... had no difficulty in again proving "that by the operation of potassium upon , it is not a metallic body that is decompounded, but the volatile alkali, and that the hydrogen produced does not arise from the potassium, as is asserted by the French chemists, but from the ammonia.""